Enhanced E911 Network Access for a Call Center Using Session Initiation Protocol (SIP) Messaging

ABSTRACT

A switched emergency call (e.g., a 911 call, an alarm company call) forwarded by a telematics call center is converted into a session initiation protocol (SIP) packetized phone call at the call center, and routed over an IP network, for presentation to an emergency services gateway, which connects to a selective router via dedicated circuits, gaining full access to the Enhanced 911 network. This provides a PSAP receiving a call from a telematics call center or other call center with all features available in an Enhanced 911 network, e.g., callback number of the 911 caller, and location of the 911 caller. Location of the caller is provided using a VoIP positioning center (VPC), queried from the call center. In this way, the switched emergency call is converted into a SIP packetized phone call and routed without further passage through the public switched telephone network (PSTN).

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to E9-1-1 emergency phone calls. Moreparticularly, it relates to emergency E9-1-1 calls using Voice OverInternet Protocol (VoIP), originating from centralized call centers.

2. Background of the Related Art

911 is a phone number legislated into law as a designated universalemergency phone number used by callers to access emergency responseservices. Enhanced 911 (E911) is defined by the transmission of callbacknumber and location information to the relevant public safety answeringpoint (PSAP). A PSAP is the endpoint of an emergency services call.PSAPs are responsible for answering emergency services calls. E911 maybe implemented for landline, VoIP, and/or mobile devices. Some PublicSafety Access Points (PSAPs) are not enhanced, and thus do not receivethe callback or location information from any phone, landline or mobile.

Many cars built today include a telematics system. The word“telematics”, in its broadest sense, relates to the combination ofcomputers and wireless telecommunications technologies. More recently,the term “telematics” has evolved to refer to automobile systems thatcombine global positioning satellite (GPS) tracking and other wirelesscommunications for automatic roadside assistance and remote diagnostics.General Motors Corp. first popularized automotive telematics with itsOnStar™ system. Mercedes-Benz offers a similar system called TeleAid™.The use of the word “telematics” throughout the current specification isintended to refer to the later definition of more recent recognition,i.e., to mean automotive telematics.

Many new vehicles are equipped with wireless-based telematics unitsproviding services controlled by voice commands. One successfultelematics system is available from OnStar Corp. (www.onstar.com).According to OnStar, OnStar brings together emergency service providers,wireless telephone, and satellite technologies to help protect a driver,and keep them connected on the road.

As part of the telematics system, a telematics unit including a cellulartelephone circuit is located within the vehicle, and powered by thevehicle's battery. Telematics units were originally analog-only, buthave migrated to analog/digital-ready, and finally to dual-modeanalog/digital. Dual-mode analog/digital telematics units operate onboth the analog and digital wireless networks.

With a suitable subscription for the use of a telematics operationscenter such as OnStar, a driver or passenger in a vehicle including atelematics unit has access to a voice-activated calling feature in theirvehicle, just in case their hand-held cell phone is lost, forgotten orhas a low battery. They can pre-purchase OnStar Hands-Free Callingminutes to use on the road. Such packages are typically billed to acredit card they keep on file with OnStar. They can order minutespackages by pushing the phone or white-dot button at any time.

Conventional telematics units are also capable of providing locationinformation to a requesting wireless network, using a Global PositioningSatellite (GPS) mounted in the vehicle, or using other locationtechnology within the wireless network. When a vehicle occupant pushes agiven button in the vehicle, essentially calling the telematicsoperations center, the action initiates the location-determiningtechnology which then transmits vehicle location to the telematicsoperations center. Moreover, if their air bag deploys, the location ofthe vehicle can be automatically reported to the telematics operationscenter. So it's only when the button is pushed to contact the telematicsoperations center, or when the telematics operations center isresponding to an emergency signal, that the telematics operations centeris provided with a location of the vehicle.

Today, most telematics companies and more generally alarm companiesmonitor signals from customers' car, home or business. The monitoring isusually centralized in a single location for customer locations acrossthe country (e.g., a station in Columbus, Ohio might monitor homesthroughout the country for a given monitoring company. In more globalcompanies, an alarm or other monitoring company might monitor alarmsignals from homes in the United States from a centralized commandcenter located in Bombay, India.

Thus, in today's global economy, when a customer places an emergencycall such as a 911 call (or automated alarm system emergency call), thecall may be routed very far away, and in some instances half-way acrossthe world. The telematics operator must then transfer the 911 call tothe relevant 911 center (public safety access point (PSAP)). However,this transfer must take place over the Public Switched Telephone Network(PSTN) because such transfer, cannot conventionally be gained to thePSAP's existing Enhanced 911 (E911) dedicated network. Moreover, notethat even the call related information (e.g., CallerID) provided withthe call would relate to the identity and location of the centralizedtelematics center—not to the callback number and certainly not thelocation of the customer originally dialing 911.

FIG. 3 shows conventional relevant systems in an emergency 911 call madevia a telematics call center.

In particular, as shown in FIG. 3, a telematics unit 101 within a cardials 911. The 911 call is serviced by a cell site of a serviceprovider, which includes a given mobile servicing center (MSC) 102. TheMSC 102 passes the 911 call on to its relevant telematics call center104 via the PSTN. The telematics call center 104 may be, e.g., anONSTAR™ call center.

The operator at the telematics call center 104 that handles the 911 callof its own subscriber obtains the identity and location information ofthe 911 caller. Based on the current location of the 911 caller, theoperator performs a query of a telematics PSAP database 106 to determinea unique 10-digit phone number of the proper local PSAP physicallyresponsible for the location of the 911 caller. The telematics PSAPdatabase 106 is essentially the equivalent of an Emergency Routing DataBase (ERDB).

The operator at the telematics call center 104 then forwards the 911caller to the PSAP by dialing its 10-digit phone number via the publicswitched telephone network (PSTN) 110.

Unfortunately, calls that arrive at the PSAP in this manner do notinclude call-back number (Automatic Number Identification (ANI)) andlocation information (Automatic Location Identification (ALI)).Moreover, the PSTN telephone 302 at the PSAP 118 is typically notanswered with the same priority as are calls that originate on its E911network. In addition, these calls are typically not recorded ortime-stamped by PSAP equipment as are calls that arrive via the E911network.

Trials have been conducted in which a local exchange carrier (LEC) haspermitted access to a selective router for the E911 network via thePSTN. In this trial, the LEC designated a specific 10-digit telephonenumber for each specific PSAP. A caller has their emergency calltransferred to this 10-digit telephone number, which is thencall-forwarded within the central office to the selective router, whichthen forwards the call to the correct PSAP based upon the digits dialed.However, this solution suffers from various security issues and has notfound favor in the LEC industry or within the PSAP community.

Other conventional technology relies on the PSAP having separate, secondset of phone equipment capable of receiving proprietary data from thetelematics center 104. But this solution would be prohibitively costlyto implement nationwide for each telematics center, not to mention takeup valuable space inside a PSAP center. Thus, the costs and disruptioncaused by the need for new hardware makes this a rather undesirablesolution.

There is the need for a simple and effective solution to providing easyand full access to the Enhanced 911 network of an emergency servicesprovider (e.g., PSAP) from users of a centralized call center, e.g,telematics call center, alarm call center, etc.

SUMMARY OF THE INVENTION

In accordance with the principles of the present invention, a method andapparatus for providing a call center with access to an Enhanced 911network supporting a public safety answering point (PSAP) comprisesdetermining a unique PSAP having jurisdictional responsibility for aphysical current location of a caller to the call center. The caller isforwarded via a switched telephone network to a Vol P call server. Theswitched telephone call is converted into a session initiation protocol(SIP) packetized phone call at the call center. A VoIP positioningcenter is queried for call routing instructions for the SIP packetizedphone call. The SIP packetized phone call is routed to an emergencyservices gateway without further passage through the public switchedtelephone network (PSTN).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an exemplary E911 architecture including E911 networkaccess provided to a telematics call center or other call center, inaccordance with the principles of the present invention.

FIG. 2 shows an exemplary call flow tracing an emergency 911 call from atelematics subscriber source to the appropriate PSAP, in accordance withthe principles of the present invention.

FIG. 3 shows conventional relevant systems in an emergency 911 call madevia a telematics call center.

FIG. 4 depicts another embodiment showing the use of SIP messaging inlieu of the PSTN for passing an E911 call from a call center, inaccordance with the principles of the present invention.

FIG. 5 shows message flow for the embodiment shown in FIG. 4.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

In a first embodiment, an emergency call (e.g., 911 call, alarm companycall) forwarded by a telematics call center is routed over the switchedPSTN to a Voice Over Internet Protocol (VoIP) call server, where theswitched call is converted to a packetized IP call for presentation toan emergency services gateway, gaining access to the Enhanced 911network. Location of the caller is determined by GPS or other technologyin the vehicle or in the wireless network, and is reported to thetelematics call center. The telematics center's call back number isprovided to the VoIP Positioning Center (VPC) via standard call set-upprocedures across the PSTN to the call server, and then from the callserver to the VPC. The caller's location may be provided to the VPC vianon-call path data links to the telematics call center. The VPC willstage the call-back and location data for subsequent transmission to thePSAP via the ALI database.

In a later embodiment, SIP messaging is used in lieu of the PSTN forpassing an E911 call from a call center. If a telematics call center hasVoIP capability, the PSTN may be avoided by routing telematics E911calls directly via VoIP between the call center and the VPC.

In a last embodiment, wireless emergency services routing keys (ESRKs)are used to route emergency calls to a telematics call center over aVoice Over IP (VoIP) network to an enhanced E911 network of a publicservice access point (PSAP).

Voice Over IP (VoIP) is a technology that has been developed as analternative telephony technology to the conventional telephony service(e.g. PSTN). VoIP takes advantage of high speed Internet data packetnetworks, and is able to provide low cost telephony services to endusers. VoIP technology emulates a phone call, but instead of using acircuit based system such as the telephone network, utilizes packetizeddata transmission techniques most notably implemented in the Internet.

VoIP phone calls are routed to a VoIP voice gateway, from which they arepassed on to their destination VoIP device. Conventional VoIP voicegateways (i.e., soft switches) are typically located in only a fewplaces across the country. A soft switch is a programmable networkswitch that can process the signaling for all types of packet protocols.Also known as a ‘media gateway controller,’ ‘call agent,’ or ‘callserver,’ such devices are used by carriers that support convergedcommunications services by integrating SS7 telephone signaling withpacket networks. Softswitches can support, e.g., IP, DSL, ATM and framerelay.

Because VoIP is Internet Protocol (IP) based, call related informationsuch as CallerlD type services may not be available or accurate. Alocation of a given VoIP device may be provisioned to be at a givengeographic location, or queried from a home location register (HLR) in amobile system.

FIG. 1 shows an exemplary E911 architecture including E911 networkaccess provided to a telematics call center or other call center, inaccordance with the principles of the present invention.

The present invention applies the switched telephone connectivity of thePSTN to route calls to a media gateway/VoIP call server 112. Theswitched call is converted into a packetized call using InternetProtocol (IP), and is routed via the internet to the ESGW 114 closest tothe appropriate selective router for the destination PSAP. The ESGWconverts the packetized IP data back into traditional TDM, and routesthe call to the intended selective router 116 via dedicated TDM trunks,where it enters the E911 network. A selective router is the node in anemergency services network that performs enhanced call routing for 911calls.

An example will be used to further illustrate the inventivearchitecture. In this example, a telematics unit 101 within a car dials911. The 911 call is serviced by a cell site of a service provider,which includes a given mobile servicing center (MSC) 102. The MSC 102forwards the 911 call on to its relevant telematics call center 104 viathe PSTN. The telematics call center 104 may be, e.g., an ONSTAR™ callcenter, and may be located anywhere in the country or anywhere in theworld.

The operator at the telematics call center 104 that handles the 911 callof its own subscriber obtains the nature of the call, as well as theidentity and location of the 911 caller. The identity and location ofthe 911 call from the subscriber is most often received by the callcenter 104 over the open phone line to their subscriber. Equipment toreceive the exact location of the subscriber is expensive, but necessaryonly at the centralized telematics call center. The thousands of PSAPsin the country do not have the same equipment, as it would beprohibitively expensive.

Based on the current location of the 911 caller, the operator performs aquery of a telematics PSAP database 106 to determine a local PSAPphysically responsible for that location, as well as a unique 10-digitphone number to access the Enhanced 911 network of that PSAP.

The operator at the telematics call center 104 handling the 911 callforwards the emergency call to a given media gateway/VoIP call server112 via the PSTN by dialing the designated 10-digit number for that PSAP

To determine the appropriate PSAP and ESGW, the VoIP call server 112queries a VoIP positioning center (VPC) 130. Using the 10-digit phonenumber dialed by the call center operator 104, the VPC queries thedatabase 134 to determine the corresponding PSAP. The VPC then assignsan Emergency Services Query Key (ESQK) to the call and relays thisrouting key back to the VoIP Call Server 112.

The VoIP call server 112 passes the 911 emergency call on to anemergency service gateway (ESGW) 114, which in turn passes the 911emergency call on to the desired PSAP 118. An ESGW resides in a VoIPservice provider's network, and is responsible for integrating thesession initiation protocol (SIP) network with the emergency servicesnetwork (TDM). An ESGW 114 network includes dedicated voice trunks toselective routers in the Enhanced 911 (E911) network for any/all PSAPsbeing served (ideally a national network). The ESGW 114 routes 911 callsto the appropriate selective router, based on the ESRN/ESQK it receives.

The selective router 116 is provisioned with emergency services querykeys (ESQKs) with ALI steering. (The ESQK is a digit string thatuniquely identifies an ongoing emergency services call and is used tocorrelate the emergency services call with the associated data messages.It may also identify an emergency services zone and may be used to routethe call through the network. The ESQK is similar to an ESRK in wirelessE911 networks.)

A subscriber location database (SLDB) 134 is also provisioned.Preferably the SLDB 134 is configured so that no modifications arerequired to the core conventional existing VoIP E9-1-1 network. The SLDB134 is used to relate a Session Initiation Protocol (SIP) UniversalResource Identifier (URI) or a telephone number to a PSAP.

In the given embodiments the SLDB 134 includes a listing of a series of“subscribers”, in which each subscriber is really a specific PSAP with adesignated 1-900-xxx-yyyy phone number. Note that the phone number doesnot need to be a 1-900 number as this is used as an example only. Thisis also a useful technique for billing the call center for this service.

In the disclosed embodiments, the address of this “subscriber” is thelatitude/longitude (lat/lon) of a centroid of the jurisdiction of therelevant PSAP. Alternatively, in datbases that use tables in lieu of GISfor routing determination, the address of the “subscriber” can be anyvalid address within the jurisdiction of the PSAP.

FIG. 2 shows an exemplary call flow tracing an emergency 911 call from atelematics subscriber source to the appropriate PSAP, in accordance withthe principles of the present invention.

In particular, as shown in FIG. 2, a caller or automated calling device101 contacts a local security monitoring company or roadside assistanceoperator or similar third party call center 104. As an example shown instep 1, a caller 101 dials 911, which is serviced through a wireless MSC102 and passed on to the relevant telematics call center, e.g., anOnSTAR™ call center. In the given example, the wireless MSC 102 may bepart of a wireless carrier's network, with the 911 call being forwardedto the relevant telematics call center 104. Alternatively, the MSC 102may be part of a large wireless network used by the telematics companyitself.

The 911 call may be placed using an SOS or similar single-press buttonlocated in a car for use in emergency situations, automatically in theevent of an accident, etc. Alternatively, the phone user may simply dial911 in a manual cell phone call from a mobile phone, either integratedinto a vehicle or entirely separate from a vehicle.

In step 2, a wireless MSC 102 routes the incoming emergency call to atelematics call center 104 (e.g., an ONSTAR™ or TeleAid™ call center).In the given example this routing includes use of the PSTN 110, thoughthis need not be the case in all applications.

The call taker at the call center 104 who receives the 911 call from thecaller 101 determines that this is an emergency call that must bereferred to the local 911 PSAP.

Thus, in step 3, the telematics call taker queries an existingtelematics PSAP database 106 to determine the correct PSAP to which thecall should be routed. Of course, to save time step 3 may be performedsimultaneous with, or even prior to, the call taker's determination thatthe call from the mobile user 101 is an emergency call.

In step 4, a telematics dispatcher dials (could be the same personand/or equipment as the call taker) a NPA-xxx-yyyy number designated forthe determined PSAP. For instance, the call taker at the call center 104then dials 1-900-xxx-yyyy, a designated number for that PSAP 118, andprepares to conduct a conference call with the caller 101 and the PSAP118.

The call is then routed, via the PSTN 110, to a designated VoIP callserver 112 (alternatively referred to as a media gateway). The mediagateway and the VoIP call server may be two distinct functionsco-located in the same unit, as in the present embodiment. The mediagateway converts TDM to IP. The VoIP call server routes the resulting IPcalls much like a traditional telephone switch routes a TDM call.

The VoIP call server 112 receives the ANI (caller ID) of the callcenter. The VoIP media gateway 112 reformats the call from time divisionmultiplex (TDM) or code division multiplexed (CDM) into sessioninitiation protocol (SIP). The VoIP Call Server rearranges the dialeddigits, putting the DID that was dialed in step iii (e.g.,1-900-xxx-yyyy) in the FROM field and putting the ANI of the call centerinto the Just-in-Time callback number (JIT CBN) field within theP-Asserted Identity in the SIP Invite. (Session initiation protocol(SIP) is an IP-based protocol defined in IETF RFCs 3261 and 2543, theentirety of which are expressly incorporated herein by reference. SIP isone of two dominant messaging protocols used by the VoIP industry.

Importantly, the VoIP Media Gateway/call server 112 converts the TDM orCDM protocol of the incoming switched network phone call to packet datausing session initiation protocol (SIP), and vice versa, meaning thatpacketized VoIP information coming from a relevant PSAP is convertedinto a switched connection with the 911 caller, terminated at the VoIPcall server 112.

In step 5, the VoIP call server 112 forwards the 911 call to the VPC 130as a VoIP call. The Invite is received by the VPC 130 for call routinginstructions.

The VPC 130 is an application that determines the appropriate PSAP,based on the location of the 911 caller 101, returns associated routinginstructions to the VoIP network, and provides the call center'sidentity and the callback number to the PSAP through the automaticlocation identification (ALI). (An ALI is a database that relates aspecific telephone number to an address. This database accepts a PSAPquery with a telephone number and responds with an address. In the caseof an ESQK, the ALI database steers (redirects) the query to theappropriate VoIP positioning center and steers the response back to thequerying PSAP).

A SIP Invite command may be used for the query from the Call Server 112to the VPC 130. The disclosed SIP Invite command preferably includes thefollowing parameters:

-   -   a) The “from” field        -   =the dialed digits from the call center (NPA-xxx-yyyy)    -   b) The “to” field        -   =911    -   c) The JIT CBN field        -   =callback number of the call center

In step 6, the VoIP positioning center 132 queries an ERDB (SLDB) 134for call routing instructions based upon the dialed NPA-xxx-yyyy number.The ERDB 134 relates the dialed number to the address of that phonenumber (lat/lon of the PSAP jurisdictional centroid) and determines theappropriate PSAP to receive the call. Within the ERDB 134, each phonenumber corresponds to a different PSAP.

In step 7, the ERDB 134 responds to the VPC 130 with the identity of theappropriate PSAP to serve the caller 101. The VPC 130 assigns an ESQKand emergency services routing number (ESRN) to the call and stages anALI record. The ESRN is a 10-digit number that specifies the selectiverouter to be used to route a call. The ALI record contains the phonenumber of the call center 104, based upon the ANI that accompanied thecall. If the call center 104 is capable of sending the ANI of the actualend user, then this can be staged in the VPC ALI record.

Further call processing is otherwise per the conventional NENA i2 VoIPstandard:

For instance, in step 8, the VoIP positioning center 130 assigns anemergency services query key (ESQK) appropriate to that PSAP, and stagesa record with the call center call back number (CBN) and call centercompany ID.

The VoIP positioning center 130 responds to the VoIP call server 112with the ESQK, emergency services routing number (ESRN), and lastrouting option (LRO). (The LRO is routing information sent by the VPC130 that provides a “last chance” destination for a call, for examplethe contingency routing number (CRN) or a routing number associated witha national call center.

In step 9, the VoIP call server 112 uses the ESRN to route the call tothe correct emergency services gateway (ESGW) 114.

The VoIP call server 112 uses the received ESRN to determine theappropriate ESGW 114 and routes the call appropriately to the correctemergency services gateway (ESGW) 114. The ESGW 114 uses the ESRN todetermine the appropriate selective router 116. For simplicity andclarity of description, only one ESGW 114 and one selective router 116are pictured in FIG. 2.

In step 10, the ESGW 114 performs media conversion by converting the SIPprotocol (and vice versa in the opposite communication direction), anduses the ESRN to route the call to the correct selective router 116,along with the ESQK.)

In step 11, the selective router 116 routes the ESQK to the PSAP 118.

In step 12, the PSAP 118 queries the automatic location identification(ALI) database 120 using the ESQK.

In step 13, the ALI database 120 steers the query to the VoIPpositioning center (VPC) 130, per previously provisioned steeringtables. The VPC 130 responds with a staged record that includes thecallback number (CBN) and call center company ID. In the preferredembodiments, no latitude/longitude (lat/lon) is sent in the ALI record,although such data could be forwarded if it is available.

In step 14, the ALI database 120 forwards the callback number (CBN) andcall center ID to the requesting PSAP 118.

FIG. 4 depicts another embodiment showing the use of SIP messaging inlieu of the PSTN for passing an E911 call from a call center, inaccordance with the principles of the present invention.

In particular, according to the embodiment shown in FIG. 4, in the eventthat a telematics call center has VoIP capability, the PSTN 110 may beeschewed by routing the telematics E911 call directly via VoIP betweenthe call center 104 and the VPC 132.

As seen in FIG. 4, the PSTN of FIG. 1 is eliminated from the call flow.In this embodiment, each PSAP is assigned a designated 10-digit numberthat is provisioned in the telematics PSAP database 106. However, unlikethe embodiment of FIG. 1, these 10-digit numbers need not be dialablevia the PSTN. Instead, they can be assigned by the participatingentities without regard to what numbers may be in use by other partiesthat use the PSTN. In fact, they do not necessarily need to be 10-digitnumbers at all. Because they never see the light of day and remain atall times internal to the telematics vendor and the VPC, thesePSAP-identifiers can be any mutually compatible predetermined format.

To accomplish this, the telematics call center includes what wouldotherwise be included at the telematics call center 104 shown in FIG. 1,but additionally a session initiation protocol (SIP) private branchexchange (PBX) or telephone switch 104B.

FIG. 5 shows message flow for the embodiment shown in FIG. 4. Inparticular, as shown in step 1 of FIG. 5, a cell site picks up andrelays a 911 call made from a wireless subscriber to the carrier'swireless mobile switching center (MSC) 102.

In step 2, the wireless MSC 102 passes the wireless 911 call to thetelematics call center 104A, which in this embodiment is associated witha SIP PBX or voice over Internet protocol (VoIP) switch 104B.

As shown in step 3, upon receipt of the 911 call, the call taker at thetelematics call center 104B accesses the local telematics PSAP database106 to determine routing (as otherwise shown and described with respectto the embodiment of FIGS. 1 and 2).

In response, the telematics PSAP database 106 provides a designated PSAPnumber for that PSAP that need not be a 10-digit number that is dialableon the PSTN.

As shown in FIG. 4, the telematics call taker dials the designated PSAPnumber and initiates a conference call, or transfers the call. However,when the telematics call taker dials the designated PSAP number, theintegrated telematics VoIP switch 104B translates the designated PSAPnumber into a specific SIP message.

The VoIP switch initiates a SIP INVITE message in which the “TO” addressis a universal resource indicator (URI) address equal to a specificmailbox at the VoIP positioning center (VPC) 132 reserved for the PSAPdesignated by the original designated PSAP number. The “Just in timeCall back Number” (JITCBN) is preferably provisioned to be thePSTN-dialable phone number of the telematics call taker at thetelematics call center 104A.

In step 5, the SIP INVITE message is passed to the VoIP positioningcenter 132.

In steps 6-8, the VPC 132 selects an ESQK, ESRN and LRO appropriate tothe PSAP designated in the SIP INVITE message, and will establish RTPbetween the SIP switch 104B and the ESGW 114 indicated by the selectedESRN.

In step 9, a voice path is established via Internet Protocol (IP)between the VoIP switch 104B and the ESGW 114.

As is otherwise described herein with respect to the embodiment of FIGS.1 and 2, the ESGW 114 performs media conversion from Internet Protocol(IP) to time division multiplexing (TDM).

In step 10, the ESGW 114 routes the call in TDM format to the designatedselective router 116 according to the ESRN or the ESQK.

In step 11, the selective router 116 determines the destination PSAPbased upon the ESQK, and routes the call to the PSAP 118 per existingtechnology.

As in the embodiments described above, the VPC 132 stages an ALI recordwhen it responds to the SIP INVITE. This record consists of the assignedESQK, plus the call back number (CBN) received in the JITCBN field ofthe SIP INVITE message, plus other data as available and as desired bythe PSAP 118, e.g., NENA ID, lat/lon, etc.

In step 12, upon receipt of the call, the PSAP 118 initiates a standardquery to the ALI database 120 per existing technology.

In step 13, the ALI database 120 routes that query from the PSAP 118 tothe VPC 132 per otherwise existing technology.

In step 14, the VPC responds to the ALI query with the staged record,including a callback number and other data as desired by the PSAP 118.

In accordance with the present invention, benefits are derived byrouting 911 calls via the Enhanced E911 network. Moreover, PSAPs canutilize all available technologies available to them in an Enhanced E911network such as CAD, selective transfer, etc. when responding to a callfrom a telematics or other call center.

The present invention makes possible the transfer of misrouted ordefaulted VoIP calls from a VoIP default call center to the appropriatePSAP via the Enhanced E911 network. In conventional systems defaultedcalls must be routed via the PSTN.

This invention saves taxpayers money by allowing PSAPs to discontinuedesignated PSTN lines. This invention also increases the speed withwhich emergency services (responders) can be dispatched and providesrecorded documentation of conversations that are typically available oncalls received via the E911 network, but not via the PSTN.

The present invention has particular relevance for use by any alarmmonitoring company, telematics call center, or emergency call centerthat monitors incoming calls. The invention has significant benefit inthe use by automotive roadside assistance call centers like OnStar™,TeleAid, etc.

While the invention has been described with reference to the exemplaryembodiments thereof, those skilled in the art will be able to makevarious modifications to the described embodiments of the inventionwithout departing from the true spirit and scope of the invention.

1. A method of providing a call center with access to an Enhanced 911network supporting a public safety answering point (PSAP), comprising:determining a unique PSAP having jurisdictional responsibility for aphysical current location of a caller to said call center; convertingsaid switched telephone call into a session initiation protocol (SIP)packetized phone call at said call center; querying a VoIP positioningcenter for call routing instructions for said SIP packetized phone call;and routing said SIP packetized phone call to an emergency servicesgateway without further passage through a public switched telephonenetwork (PSTN). 2-12. (canceled)